If the site only needs jquery for one thing and it can be done using an older smaller version of jquery, then could you include the older (smaller) version to save bandwidth and potentially have a greater number of users that already have an older version cached?
So for instance
jquery-1.6.1.min.js is 89k
Where
jquery-1.2.6.pack.js is 31k
The site performs with the smaller older version, so why not use it as it is less in file size?
